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MS2/water temp/fan control

t11 - 25/5/13 at 05:54 AM

Hi all.....I'am running an MS2on a toyota engine with all the correct sensors with everything running fine apart from the fan control from the ecu....its set to come pon at a certain temp and then cut off a a normal car would do but as the water temp sensor fits in the engine it will only tell the ecu what the temp is there and not in the rad, so after a run and the gauge showing 90deg the fan was on so turned off the engine and turned the ignition back on to see how long it would be before the fan cut out, the rad was stone cold after 10 mins but as the sensor is in the engine and the gauge showing 80deg and still hot the fan was still on, how can I get round this ?.....a normal car the fan switch is in the rad and the fan will keep running un-till the temp is correct with the ignition off.........any idears

ashg - 25/5/13 at 06:45 AM

sit there with the engine at idle and let the fan actually cool the engine down (not the rad!). whats the point of running the fan if the engine is not running to push the water round.

britishtrident - 25/5/13 at 07:42 AM

I can't help you with doing it via software settings but you could do it by changes to the wiring.

Before doing anything can I ask what your fan cut in and cut out temperatures are and what is the thermostat temperature is ? as is likely they are too close to thermostat temperature. The fan should cut in and cut out above the thermostat starts to open temperature. If the thermostat starts to open at around 88 to 90c then the fan shut be set to cut in at around 97c and cut back out at about 93c.

If you want to do it by changing the wiring you could do it by either wiring the fan relay through a time delay board
Timer relay board adjustable 1 - 10 minutes (in 1 minute steps) | eBay

Alternative an old fashioned fan swith in the radiator.

britishtrident - 25/5/13 at 07:48 AM

quote:
Originally posted by ashg
sit there with the engine at idle and let the fan actually cool the engine down (not the rad!). whats the point of running the fan if the engine is not running to push the water round.

One of the reasons manufacturers to it is to reduced heat soak due to high under bonnet temperatures which can cause problems with hot starting.

If the coolant is above the thermostat opens temperature the coolant will continue to slowly circulate because of the thermo-syphon effect -- back in the pre-WWII era a lot of cars didn't have water pumps and were cooled entirely by thermo-syphon circulation.

rusty nuts - 25/5/13 at 08:07 AM

The way I see it is you have coolant in the engine to cool the engine so having the sensor in the engine which measures actual engine temperature, controlling the fan via the ECU should be better than having a fan switch in the rad which only works when the rad gets hot. I'd like a pound for every engine I've seen overheating due to a stuck or faulty thermostat or an air lock when the rad isn't hot enough to trigger the fan switch

britishtrident - 25/5/13 at 09:08 AM

quote:
Originally posted by rusty nuts
The way I see it is you have coolant in the engine to cool the engine so having the sensor in the engine which measures actual engine temperature, controlling the fan via the ECU should be better than having a fan switch in the rad which only works when the rad gets hot. I'd like a pound for every engine I've seen overheating due to a stuck or faulty thermostat or an air lock when the rad isn't hot enough to trigger the fan switch

Chicken and egg trouble is if the coolant isn't circulating the fan won't cool the engine much anyway and having the rad warm has advantages in cold weather.

These days at lot of tintop fans don't cut in until the engine temp reaches 105c which is just crazy, if the rad isn't holding pressure the engine can be boiling away but the temperature gauge is on "N" and fan hasn't cut in.

Yesterday I fixed a Rover 75 that had two head gaskets fitted in the last 3 months when it came in it would almost empty the rad in 5 miles running.
All that had been wrong with was the rad cap wasn't holding pressure and the top hose was leaking (couldn't be seen as it was a steam leak) and the O ring at the water pump inlet tube was leaking because some bright spark had left the tube support bolts off. I put the pressure tester on took it up to 20psi it found the leaks fixed them and drilled a 1/8" hole in the thermostat bled the system.

matt_gsxr - 25/5/13 at 02:39 PM

I don't bother with the MS fan control and just run with a temperature controlled switch in the radiator.

BaileyPerformance - 30/5/13 at 08:01 AM

The stat is closing and the water has stopped circulating so the engine temp remains high and the rad will cool.

Fit a low temp stat (80ish) and set the fan setting on at 95 off at 90. You set this in the outputs menu, output iac1a.(I used one of the idle outputs to drive the fan relay)

t11 - 8/6/13 at 06:13 AM

Hi all thanks for your thoughts, at the moment I have a problem with my laptop so can't alter the fan setting so need to get that sorted first...Dale the thermostat is a 82deg which is standard for the 3sge engine and due to its size nothing else fits,but I still need to get my settings from you after the rolling road set up last November I will be in touch soon on that one.......Gordon

rx7locost - 8/6/13 at 03:15 PM

FYI, I have the MS fan switch to come on ~5 deg C above the thermostat rating. And have ~3 deg C hysteresis programmed into the MS. My theory is that if the car is moving and air is flowing through the radiator, the fan will not come on at all. Once at a stop, the fan should kick on and off as needed only when the thermostat is open. In actual practice, when I pull up to a traffic light and stop, after about 1/2 minute, I can hear the fan come on. It runs for a short while and then shuts off. So I know it is working in the manner it was intended. My temp sensor is located near the thermostat housing. In my case, there is a 2nd thermostat that is in the engine block that only drives the gauge. I can compare engine temp (dash gauge) to Megasquirt's sensed temp.

Most modern cars that I am familiar with, control the fan from the ECU and use the engine temp sensor, usually located at the thermostat housing. There is no separate separate sensor/switch for the cooling fan in the radiator.